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Background The excess adiposity, even in the absence of diseases, is responsible for a decline in pulmonary function, which is considered a predictor of mortality and a risk factor for diseases in several epidemiological studies. However, studies on the association between obesity and pulmonary function have found only few associations or inconclusive results. The aim of the study is to evaluate the association between body composition and spirometric parameters, comparing simple obesity measures such as body mass index (BMI) and waist circumference with more precise body composition measurements such as dual-energy X-ray absorptiometry (DXA) and air-displacement plethysmography (BOD POD). Methods This is an observational, cross-sectional study that used data from the 1978/79 Ribeirão Preto birth cohort (São Paulo, Brazil). The study included 1746 participants from the 5th follow-up of the cohort. Linear regressions were calculated to evaluate the association between BMI, waist circumference, waist–height ratio (WHtR), BOD POD- and DXA-measured fat mass percentage, and spirometric parameters FEV1, and FVC. Results For every 1-kg/m2 BMI increase, FVC decreased by 13 ml in males and by 6 ml in females and FEV1 decreased by 11 ml and 5 ml, respectively. Regarding body composition measurements, for a 1% increase in fat mass assessed by BOD POD, FVC decreased by 16 ml in males and by 8 ml in females and FEV1 decreased by 13 ml and 7 ml, respectively. Hence, negative associations between body measurements and FEV1 and FVC were observed in both genders, especially when using the fat mass measurement and were more expressive in men. Conclusion The anthropometric and body composition parameters were negatively associated with the spirometric variables FVC and FEV1. We have also observed that simple measures such as waist-height ratio were sufficient to detect the association of body composition with pulmonary function reduction.

Clinical asthma appears to be less severe when diabetes mellitus is superimposed. To examine whether insulin influences the development of allergic reactions in the airway mucosa antigen challenge, normal and diabetic rats sensitized against ovalbumin (OA) were used. Compared with controls, animals rendered diabetic by the injection of alloxan presented markedly decreased cell yields from bronchoalveolar lavage after OA challenge. The impaired response was not related to antibody production because enhanced IgE antibody titers of the same magnitude were found in both control and diabetic animals. Similarly, the mechanism underlying the inhibited responses could not be ascribed to hyperglycemia or intracellular glucopenia, first, because correction of blood glucose levels through fasting did not restore the decreased response, and second, because administration of 2-deoxyglucose, which blocks glucose utilization, did not affect the bronchoalveolar reaction to OA challenge in normal animals. Reversal of the impaired responses was attained by treatment of diabetic animals with insulin. There is evidence that insulin exerts proinflammatory effects. We conclude that insulin might modulate the inflammatory component of asthmatic responses.

Nocturnal worsening of asthma is very common and employed in clinical practice as a marker of asthma severity. The fall in overnight lung function can reach 50%. Several mechanisms contribute to this circadian (24 h) variation. Cortisol, steroid responsiveness, vagal tone, leukotriene, airway inflammation and airway hyperresponsiveness vary in a circadian fashion and have been described as potential mechanisms. Studies on the ability of corticosteroids to block circadian recruitment of inflammatory cells show that a single corticosteroid systemic dose in the afternoon results in a significant pancellular reduction in bronchoalveolar lavage cytology at 4: 00 h and a reduction in the overnight fall in FEV1. The same single dose in the morning or night does not lead to significant improvement. Further studies on chronotherapy of asthma have revealed a rapid and time-dependent effect of inhaled steroids. A single dose of inhaled steroid in the afternoon has a protective effect against asthma worsening in the same night. Chronotherapeutic principles are also applied with other than corticosteroid drugs in the regular asthma treatment.

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